This paper presents a front-unit-following control method for a snake-like robot using screw drive mechanism. The operators are required to command only one unit in the head, then commands for the rest of the units are automatically calculated to track the path of the preceding units. Asymptotic tracking error is investigated based on a Lyapunov approach for the case of a constant curvature. Furthermore, the effectiveness of the proposed method is investigated by computer simulations and laboratory experiments.
Robot control systems consist of a feedback controller and reference motion pattern. They are designed based on robot dynamics and coupled with each other. So far, we have proposed controller design method based on orbit attractor of nonlinear dynamics. Because the controller yields one motion for one robot, we can assume that the controller includes information of motion and body elements. If those elements can be decomposed from the controller, a new controller will be easily designed by combination of the these elements. In this paper, we propose a motion and body elements design method with Lagrange's method of undetermined multipliers based on robot dynamics, and combination design method of the new controller using the elements. Effectiveness of the proposed method is evaluated by experiments with tapping dance robots.
A large motion data has been stored by using a motion capture system such that humanoid robots or CG characters can perform human-like behaviors. However prerecorded data is not reused efficiently since it is difficult to retrieve a specified motion data from a large dataset, and to modify the motion data to fit desired motion patterns. We have studied an imitative learning model based on symbolization of motion patterns using Hidden Markov Models (HMMs), where each HMM (“motion symbol”) abstracts dynamics of some motion patterns and can be used for motion recognition and generation. So in this paper, we propose an novel framework to retrieve and generate of human motion data, which consists of original motion data, motion symbols and motion words. Each motion dataset is labeled with motion symbols. Moreover an association between motion symbols and motion words is stochastically formed. The association makes it possible to derive motion symbols from motion words and to search for motion datasets using the motion symbols. The motion symbols can also generate motion data. Therefore the framework can provide the desired motion data when only the motion words are input.
This paper describes a novel approach to modeling behavioral communication for humanoid robots that interact with their partners. Communication is established based on reaction through recognition of motion patterns of partners. Previous work of symbolization of motion primitives using Hidden Markov Models (HMMs) allows robots to recognize the observation and generate their own behaviors separately. In this paper we proposes a hierarchical model for communication, where HMMs in a lower layer abstract motion primitives of a robot and its partner and HMMs in a upper layer abstract interaction patterns. In the upper layer, output is recognition result of current interaction and input is generation of interaction. Shortcut between the output and input maintains the current interaction and realizes behavioral communication between the robot and the partner. Experiments of a humanoid robot interacting with its partner in a virtual world validate our principle of fundamental communication.
We have been studying a remote-collaboration system called SCOPE (sight collaboration by projection effect) featuring image projecting and capturing capabilities as implemented in a maintenance robot. With the help of SCOPE and a remote support person, an on-site worker can perform maintenance very efficiently. In this paper, we propose a mobile SCOPE named Campro-R that can significantly expand the area of activity of the conventional SCOPE. To enable an on-site worker to share the field of view of a remote support person, we developed a technique for aligning the optical axes of a camera and a projector. We present experimental data that demonstrates the validity of our optomechanical design. Finally, we show that the Campro-R enables workers to continuously share their field of view, no matter where the Campro-R moves.
In this paper, we propose a method to recognize periodic gestures from images. The proposed method uses a amplitude spectrum and a phase spectrum that are obtained by applying Fast Fourier Transform (FFT) to a time series of intensity images. FFT is applied to each pixel of low-resolution images. The method consists of 2 steps. First, the method detects periodic motion regions from the amplitude spectrum. Secondly, the method uses the phase spectrum in the detected periodic motion region to classify the gestures. The proposed method is robust to lighting conditions and individual differences in skin color because it does not rely on color information. Additionally, the proposed method is possible to recognize periodic gestures when multiple target regions, for example, two or more individuals are observed. Several experiments are performed to demonstrate the effectiveness of the proposed method.
This paper discusses development of a four DOF (Degree of Freedom) high speed parallel mechanism for electronic part mounters. First, the concept of the Virtual Force Redundancy (VFR) is proposed based on an analysis of a typical four DOF pick-and-place motion. VFR is defined as; when the DOF of a robot's endpoint motion is decreased in a certain region, the robot is regarded to have VFR in the region. Second, a noble structure of a four DOF high speed parallel mechanism is proposed using the newly designed Constrained Differential Drive Mechanism (CDDM) based on the VFR concept. The dynamics of CDDM is analyzed to investigate the theoretical maximum acceleration. Then, a trajectory planning and a position controller with a low level velocity controller are embodied for the proposed mechanism. Usually, adopting velocity controller for all the joints of parallel mechanism with force redundancy could cause large internal force because of the over-constraint property. However, the proposed parallel mechanism with VFR does not cause such problems because it does not have the over-constraint property. Finally, the maximum acceleration of CDDM and the cycle time of pick-and-place motion are measured using a prototype in order to investigate the validity of the proposed high speed parallel mechanism and the VFR concept.